Rheumatoid Factor (RF)
Rheumatoid factor (RF) is an antibody that can bind to your own immunoglobulins. This blood test measures how much RF is present.
Because RF is one of the tests used to help evaluate joint pain, stiffness, and swelling that might point toward rheumatoid arthritis or related autoimmune conditions. It also appears in other situations, so it is most useful when combined with symptoms and other tests. Tracking it can add context to a broader autoimmune workup.
An elevated RF can be associated with rheumatoid arthritis and some other autoimmune or chronic inflammatory conditions, and higher levels may reflect more active disease in some people. However, RF can also be positive in healthy individuals, in some infections, and more often with older age, so a positive result is not proof of disease on its own.
A negative or normal RF is generally reassuring, though some people with rheumatoid arthritis have a negative RF (so-called seronegative disease). Your clinician weighs it against your symptoms and other results.
A negative or low result is typical. Interpretation of any positive result should be done by your clinician alongside your symptoms and additional testing such as anti-CCP.
Sources
Educational context only, not medical advice or a diagnosis. Reference ranges vary by lab, age and sex; always discuss your results with a clinician.